Ribbon oscillograph



Feb. 2, 1943. c. R. sKlNNER l y i 29,309,994

RIBBON OSC ILLOGRAPH .Filed Oct. 28, 1959 42 Sheets-Sheet 1 V 1 -T 2:q. 1 2,6 /f/ 24` Mfrs/enc jo l Agen/,gn 36 j I' 57 7 l-Innunnnnnnjgg m/VENToRT CLIFTON R. SK/NNER.

ATTORNEYS.

2 Sheets-Sheet 2 C. R. SKINNER v RIBBON oscILLoGRAPH Filed oct. 2a'. 1959 Feb. 2, 1943.

w v INVENTOR, cL/FroN R. sk/NNER.

TTORNEs.

Patented Feb. 2, 1943 UNE'E'ED STTES P'iiil' OFFICE RIBBON OSCILLOGRAPH Clifton R. Skinner, San Francisco, Calif.

Application October 28, 1939, Serial No. 301,789

9V Claims.

My invention relates to ribbon oscillographs, and more particularly t such an oscillograph ideally adapted for use in sound recording or for similar purposes.

Among the objects of my invention are: To provide a ribbon oscillograph of simple construction; to provide a ribbon oscillograph in which dimensions and spacings may be rigidly controlled; to provide a ribbon oscillograph which Will have substantially uniform characteristics when produced in quantity; to provide a means and method of controlling spacings in a ribbon oscillograph; to provide a ribbon oscillograph wherein temperature changes will produce minimum and predictable distortions; and to provide a means of producing ribbon oscillographs of uniform characteristics.

Referring to the drawings:

Fig. 1 is a longitudinal sectional View of a pre- I ferred form of my invention, together with a schematic layout of a recording system.

Fig. 2 is a cross sectional View taken as indicated by the line 2 2 in Fig. 1.

Fig. 3 is a partial sectional View, much enlarged, showing a ribbon seat.

Fig. 4 is a partial plan view of the ribbon spacing and supporting means.

Fig. 5 is a longitudinal sectional view of a modification of my invention utilizing a permanent magnet field.

Fig. 6 is la cross-sectional View, taken as indicated by the line -i in Fig. 5.

Fig. 7 is a fragmentary sectional View showing the construction of the ribboned tension means used in the device of Fig. 5.

Referring directly to the drawings for a better understanding of my invention, a circular base plate l of magnetic material is provided, on one side of which is mounted a flat foundation member 2 of non-magnetic material preferably metal, insulated from the base plate by an insulating spacer li. Foundation member 2. is provided with a hollow truncated cone 5 extending outwardly from the foundation member coaxial With the axis of the base plate l. At one side of the cone, preferably in line with the long dimension of the base plate l, is a segment 6 of insulating material which is so inset into the side of the cone that one surface l thereof forms a portion of the annular truncated surface 9.

An oscillograph ribbon is to be stretched across the truncated surface 9 and the space enclosed thereby, and it is important that there will be two free portionsof the ribbon adjacent, parallel,

and in exactly the same plane, together with means for conducting current in one direction through one portion and in the opposite direction through the other portion. I therefore cut opposite parallel slots in the upper surface of the cone. The cuts on one side of the cone are made wholly through insulating material and on the other side through metal.

After the preliminary cuts have been made vas described, and located so that a diameter of the opening in the cone is included between .the cuts, the foundation member and the cone are removed from the milling machine and placed in a lathe. A shelf I2 is then cut around `the inner periphery of the cone, preferably having a ccnic surface whose base angle is greater than that of cone 5. rThe inner edge of this shelf is in a plane exactly parallel to foundation member 2, and so that the distance between this edge and the outer surface of base plate I may be accurately determined.

An os cillograph ribbon of the proper dimensions to nt the slots previously described is then strung across the truncated surface and o-peningof the cone. The ribbon is arranged in the form of a U. One leg Iii is attached to a windlass I5 mounted on a connection block I6 insulated by an insulating plate I8 from foundation member 2. Likewise, the opposite leg I'I is attached to a second windlass I9, o-n a second connection block 20, likewise insulated from base plate 2 by spacer I8. The heads of the windlasses are placedvrelatively close together, so that the angle of spread between the legs at notches I0 and the Windlass heads Will not be too great. The legs of the ribbon are then placed inslots Il so that as they cross the truncated surface of the cone they will rest, not on this surface, but solely on shelf l2, with rm contact at the higher edge thereof. The legs are spaced by spacing lug II between the cuts, and both legs are maintained inthe same plane by resting on the accurately machined shelf.

Loop 2l of the ribbon passes around a pulley 22 which, through a loop spring 24, is attached to a loop windlass 25 on the opposite side ofthe cone. Thus, by manipulation of the three-Windlasses, predetermined tension may be lplaced upon the ribbon as desired in the obtaining of the the leg Windlasses I5 and I9-so that current is conducted through one leg of the ribbon across the cone opening and back through the other leg, the ribbon being shorted on the loop side thereof by contact with the cone material, the insulation on the leg side being provided by insulator E.

For operation, the magnetic field across the ribbons may be provided by an assembly comprising a pole tip 3l passing through a central aperture in base plate I and mounted on base plate I with a portion 32 entering the ribbon cone 5, this portion having surfaces 33 converging to provide a narrow pole area "it adjacent and following the extent of the ribbon legs. Inasm'uch as the inward extent of this pole tip is determined by the contact with the outer surface of base plate I, and the shelf I2 has been accurately machined, with respect to a predetermined dimension, it can readily be seen that the air gap between the pole area 34 and the ribbons may be accurately regulated. Pole tip SI is also provide-d with a central light aperture 35 surrounding the axis of the tip and cone.

The magnetic circuit is completed by a hollow magnet core 36 having a core area 3l opposed to pole area Si on the other side of the ribbon and spaced therefrom. Hollow core t is also provided with a light aperture 39 registering with the equivalent aperture in the pole tip. Core 36 is attached to pot dil, of magnetic material, to which base plate I is applied as a cover, and a eld winding 4I is wound around core 35 and energized by any convenient source d2 to provide a magnetic flux across the ribbon at right angles to the plane thereof. The core area spacing from the ribbon may be predetermined by proper nt and dimensions of the pot and base plate.

'A schematized sound recording set-up for the oscillograph of my invention is shown in Fig. l, for Variable area recording. Here, light from source i) is collected by condensing lenses 5I and thrown through light apertures 35 and 39. Thus, light will pass between legs It and Il of the ribbon and through hollow core 36, through objective lens 52, onto photosensitive iilm 54 driven by any well known means 55.

In order that variable area recording may be accomplished, I provide a vertical masking slit 56 mounted on the end of hollow core 36, this slit being just wide enough to mask off all light passing around the outer edges of the ribbon legs lll and I'I at minimum spacing of the ribbon legs. On the other side of objective lens 52, and preferably fairly close to the film 54, I position a defining' slit 5'! which extends parallel to the motion of the ribbons. In one preferred set-up the masking slit 56 may be .009 in width, and the defining slit may be .001" or less in width. The operation of a ribbon oscillograph of this type is well known. In the strong magnetic iield any current through the ribbon travels in one direction in one leg of the ribbon and in the opposite direction in the other, thus causing the ribbons to approach each other or repel each other in accordance with the direction of the field flux as determined by the direction of current flow around the field coil. When the ribbon legs become spread the width of the light beam thrown on the lm 54 is greater than when the ribbon legs approach each other. when varying current is supplied to the ribbon with a steady flux through the air gap between pole areas, there will be photographed on film 54 a variable area record. Obviously, however, I do not wish my invention to be limited to variable area recording or even to sound recording Thus,

aeoaeei alone. My invention resides primarily in the oscillograph construction which may be used for any purpose, for which such oscillographs may be suitable. Nor do I wish to be limited to the dimensions given herein as they are illustrative only of one preferred form and may be changed within the knowledge of those skilled in the art, for any desired purpose. rIhe essence of my invention lies in the mounting of the ribbon in such a manner that it will lie parallel and nat, on solidly connected ribbon seats which have been accurately machined and accurately spaced from cooperating surfaces. v

I further wish to point out that the support of the ribbons on opposite sides of a solid com'- cal structure allows temperature characteristics to be accurately predetermined, inasmuch as these temperature changes will be symmetrically applied to both legs of the ribbon simultaneously.

In Figs. 5 and 6 I have shown a modification of my invention wherein the foundation member 2 is completely discoidal in shape instead of in bar form, as shown in Figs. 1 and 2. The disc is mounted on the base plate and insulated therefrom by insulating spacer ll, as in the first embodiment, and is provided with the same cone 5 and magnetic pole tip 3|. In order to stabilize the disc a heavy exterior rim di! is provided. The U-shaped ribbon is stretched across the cone 5 in exactly the same manner as described for the previous embodiment, but in this case it is very desirable to bring out all ribbon adjustments to the opposite face of base plate l, because in this embodiment the magnetic field is provided by a cylindrical permanent magnet 60. This magnet is provided at each end with ground faces 6I, and is securely held in a cylindrical casing 52 of non-magnetic'material, such as brass, for example. The brass casing E2 extends past the ground faces 6I to provide a groove for the reception of base plate I at one end of the magnet 60 and an end plate 6d of magnetic material at the other end thereof, both secured in place by screws 65. End plate 64 is provided with the hollow core 36 of magnetic material which carries the magnetic flux to the ribbons. Of course no field winding is necessary.

Inasmuch as a permanent magnet will lose a percentage of its magnetism if the air gap is increased after magnetization, it is highly desirable that once base plate I and end plate Si are secured in place and the magnet magnetized, that neither of these plates be removed except for replacement of the ribbon. Accordingly, I have designed this embodiment to carry all ribbon adjustments to the outside of the magnetic structure so that these adjustments can be changed without breaking the set air gap. Consequently windlasses i5 and IS pass through foundation member 2 and base plate I in an insulating bearing E6, and each one is provided with a connection lug 6l on the outside of base plate I. No windlass is used on the pulley 22 as in the former embodiment, but a lever @il is provided and mounted on a pivot 'it at one end thereof, projecting from the inner surface of foundation member 2. The other end of the lever is free to move over the foundation member surface, limited only in its arc by a retainer bracket l I.

Pulley spring 24 is attached to lever 89 intermediate the ends thereof, and the lever is moved against the pull of the pulley spring by rotation of a lever screw 'I2 passing through the base plate I and foundation member 2 and terminating in a coned surface 'lil bearing against the outermost end of lever ES. Thus, if the screw i2 is rotated the coned surface will force lever 69 to turn on its pivot and place greater or less tension on the pulley. I have shown lever 69 as being of insulating material in order that screw l2 need not be mounted in an insulating bearing.

With the construction just above outlined, tension on each end of the ribbon may be individually adjusted from the outside of the assembled casing, and tension on the pulley 22 may likewise be adjusted from the outside of the casing. Thus, I have provided a permanent magnet structure wherein all adjustments can be made without breaking the magnetic air gap, and have also provided a circularly symmetrical foundation for the ribbon.

I claim:

1. An oscillograph ribbon assembly comprising a foundation member of non-magnetic material, a hollow non-magnetic support arising from said foundation member and terminating in an upper surface, a shelf parallel to the extent of said foundation member cut into said upper surface and the interior wall of said support, a ribbon extending across the top of said support and returning to provide adjacent parallel legs on each side of the largest diameter of the interior space of said support, means for insulating the legs of said ribbon on one side of said support, said means having a surface forming a part of said shelf, means integral with said support, and means integral with said insulating means for accurately spacing said ribbon.

2. Apparatus in accordance with claim 1, with means on said foundation member for applying a tension to said ribbon, and means for applying a strong magnetic eld across said ribbon legs at right angles to the plane thereof.

3. Apparatus in accordance with claim 1, wherein the foundation member of non-magnetic material is a disc formed integral with said cone.

4. Apparatus in accordance with claim 1, wherein the foundation member of non-magnetic material is a disc formed integral with said cone, said disc having a peripheral stiiening ring integral therewith.

5. Apparatus in accordance with claim 1, wherein said ribbon assembly is applied to a magnet structure to give a magnetic field crossing the plane of said ribbon, together with means for changing the tension on said ribbon, said latter means being operable from the opposite side of said foundation member from said ribbon and said cone.

fil

6. An oscillograph ribbon assembly comprising a foundation member of non-magnetic material, a non-magnetic hollow support arising from said foundation member and having a shelf parallel to the extent of said foundation member cut into the upper surface of said support and the interior `-va-ll of said support, a ribbon extending across the open end of said support and returning to provide adjacent parallel legs on each side of a diameter of the interior of said support, and slot means spacing said legs cut into the top of said support to a depth whereby said ribbon rests entirely on said shelf.

7. An oscillograph ribbon assembly comprising a foundation member of non-magnetic material, a hollow truncated cone arising from said foundation member, a ribbon extending across the upper open end of said cone and returning to provide adjacent parallel legs on each side of a diameter of said open end, an insulating insert in said cone positioned beneath the legs of said ribbon on one side of said cone, said cone and said insert having opposite pairs of slots for receiving and spacing said ribbon.

8. An oscillograph ribbon assembly comprising a foundation member of non-magnetic material, a hollow truncated cone arising from said foundation member, a ribbon extending across the upper open end of said cone and returning to provide adjacent parallel legs on each side of a diameter of said open end, an insulating insert in said cone positioned beneath one end of the legs of said ribbon on one side of said cone, said cone and said insert having opposite pairs of slots for receiving and spacing said ribbon, all of the contacts between said ribbon and said cone and insert being in a common plane.

9. An oscillograph ribbon assembly comprising a foundation member of non-magnetic material, a hollow truncated cone arising from said foundation member and having a shelf cut into the upper surface of said cone and the interior wall thereof, a ribbon extending across the upper open end of said cone and returning to' provide adjacent parallel legs on each side of a diameter of said surface, an insulating insert in said cone positioned beneath one end of th'e legs of said ribbon and having a surface forming a part of said shelf, said cone and said insert having opposite pairs of slots for receiving and spacing said ribbon in said shelf, said shelf having a conicalY Y surface whose angle is greater than that of said truncated cone whereby edge contact only is made between the shelf and ribbon as the ribbon leaves the shelf to cross the interior of said cone.

CLIFTON R. SKINNER. 

